Freight is now commonly transported by a variety of means, for example by truck, trailer, rail, ship and by air. Freight is also commonly stored in warehouses or other storage facilities. There is always a danger that due to the nature of the freight itself, or to external factors, the freight may catch fire. If not detected, the fire may spread to other freight and to other parts of the aircraft, vehicle or storage facility. This is particularly undesirable in aircraft, where the consequences of a fire may be catastrophic. It is therefore desirable that fire originating in freight is quickly detected.
In many instances, however, the freight will not be visible to staff or crew so it will be difficult easily to identify if and where a fire may have started. Some aircraft, vehicles and storage facilities are provided with fire detection systems which incorporate static fire detectors. These systems may provide an indication of a fire in the aircraft, vehicle or storage facility, but they may not detect the fire at an early stage. This is particularly so if the freight is being transported or stored in containers or pallets, commonly referred to as Unit Load Devices (“ULDs”). In this case a fire may have started within a ULD but the static, external detectors may not sense that fire very quickly. By the time smoke or fire penetrates the walls of the ULD and triggers the fire detection system, the fire may have developed to a significant degree making it difficult to control the fire and, in aircraft based systems, giving only limited time for the aircraft to be landed safely. Moreover, these fixed systems do not provide staff or crew with information regarding the nature of the goods which have caught fire, or other information which may be of use to the staff or crew when deciding how best to deal with the fire. The fixed system may also not provide a particularly accurate indication of the location of the fire. The present disclosure seeks to address at least some of these issues.